Flashcards in ⭐️SP12/SP13-Magnetism, Motor Effect And Electromagnetic Induction Deck (58)
What is a permanent magnet?
A magnet that’s always magnetic
What is a magnetic field?
The space around a magnet where it can attract the materials iron, steel, nickel and colbalt
What is an induced magnet?
Where a piece of magnetic material is in a magnetic field and becomes a magnet its self and stops being a magnet when taken out
What can you use to find the shape of a magnetic field?
Using plotting compasses
Give examples where magnets are used
Electric motors, generators, loudspeakers and things like for latches am life holders
How do plotting compasses work?
The needle is a very small magnet and this points to the earths North Pole because the south is attracted to it
Why are compass needles weighted at one end?
To keep them level
What is the evidence for the earth’s magnetic field?
The behaviour of compasses
What is the earths magnetic field caused by?
Electric currents in the molten outer core made of a mixture of iron and nickel
Explain the magnetic field outside a solanoid
The field outside is weaker because fields from one side of the coil tend to cancel court fields on the other side of the coil
Explain the magnetic field inside a solenoid
The field is very strong because the individual fields add together to form a very strong field
What is an electromagnet?
A coil of wire with a current flowing through it
What happens of you put iron in an electromagnet? What does the iron become?
You make the magnetic field stronger, the iron becomes a temporary magnet because it’s only magnetic while the field from the electromagnet is affecting it
What is caused when a current flows through a wire?
A magnetic field
What does the direction of a magnetic field on a wire carrying a current depend on and what happens of this changes direction?
Depends on the direction of current and if this changes direction, so does the direction of magnetic field
What does the strength of a magnetic field around an electrical wire depend on?
The size of the current so the higher the current the stronger the field
Where is the magnetic field around a wire strongest?
Closer to the wire
What is a solanoid?
A coil of wire with a magnetic field around it
What happens when a wire is placed between two magnets?
It experiences a force as the current created a magnetic field and this interacts with the magnetic field between the magnets
When is the force a wire carrying current the greatest?
When is the force at 0?
When the wire is at right angles to the magnetic field produced by the magnets (as the wire has to be between two magnets to feel the force in the first place
0 when the wire is in the same direction as the magnetic field
What is the motor effect?
When a wire carrying a current experiences a force when placed between two magnets
What does the direction of the force in a wire carrying a current between two magnets depend on?
The direction of the magnetic field and the current
How can you use Fleming’s left hand rule?
To determine the direction if the current in the motor effect so:
The force is the thumb F
Magnetic field is the index finger B
The current is the index finger L
How do you find the force on a conductor carrying current at right angles to the magnetic field? Use units
Force (N) = magnetic field strength (N/ Am) or ( Tesla (T)) x current (A) x length (m)
F = B x I x L
What causes the rotation in electric motors?
The force on a conductor in a magnetic field
What are carbon brushes on an electric motor used for?
Make electrical contacts between the circuit and motor
Describe how an electric motor works
There is a force in each part of the wire carrying a current in the magnetic field and so using a coil with many turns of the wire increases the total force turning the coil
What does the split ring commutator do?
It ensures the force on the coil always turns it in the same direction by making the current is always flowing in the correct direction to make the coil continue to spin
What can a changing magnetic field induce?
A voltage or potential difference in a wire causing a current to flow